The background description provided here is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
Substrate processing systems may be used to etch film on a substrate such as a semiconductor wafer. The substrate processing systems typically include a substrate processing chamber, a gas distribution device and a substrate support. During processing, the substrate is arranged on the substrate support. Different gas mixtures may be introduced into the substrate processing chamber and radio frequency (RF) plasma may be generated to activate chemical reactions. The RF plasma may include an inductively coupled plasma (ICP) or a transformer coupled plasma (TCP). The ICP or TCP may be provided by a plasma source as a result of current being supplied to charge one or more coils of the plasma source. The plasma source includes an upper portion of a substrate processing chamber and the one or more coils.
Electronegative gases, such as nitrogen trifluoride (NF3), may be used to etch semiconductor films, which may be formed of silicon nitride (SiN). Use of the electronegative gases can result in non-uniform etching caused by non-uniform plasma densities (or poor plasma uniformity) within the upper portion of the substrate processing chamber. The poor plasma uniformity is due to localized generation of electrons near the coils of the plasma source and a high concentration of negative ions replacing the electrons. To improve poor plasma uniformity, a flow rate and/or pressure of the electronegative gases may be reduced. However, reduction in flow rate and/or pressure can reduce the overall performance of the etching process.